Discussion
Total splenectomy is a proven and effective method for the treatment of
patients with moderate to severe HS3. The spleen is
the largest peripheral lymphoid organ in the body, it is an
indispensable immune barrier when the body receives external viruses and
bacteria. The absence of spleen might lead an infection outbreak. For
pediatric patients, possible postoperative aggressive complications such
as OPSI and surgical trauma have been a long-term problem for physicians
and patients. In 1973, Maddison7 proposed splenic
artery embolization as a minimally invasive procedure for the treatment
of hypersplenism that solves the problem of severe trauma.
Spigos8 et al. developed transcatheter partial splenic
embolization (PSE) in adult HS to preserve the immune function of the
spleen5,6. However, PSE has not been widely promoted
in pediatric patients because of the poor controllability of the extent
of PSE embolization.
In our study, all the patients had moderate or severe HS. The success
rate of splenectomy and SPSE was 100%. Postoperative hemolysis was
significantly improved, no further transfusions were performed in our
patients. Previous studies had shown that PSE was effective in reducing
the degree of hemolysis while maintaining the phagocytic function of the
splenic remnant, and the selective destruction of the spleen to
defective red blood cells5. In this study, based on
the unique anatomy of the spleen and splenic artery, selective
embolization of grade 2 to grade 3 arterial branches was performed in
the spleen by intraoperative angiography. Measuring the embolic artery
blood flow velocity and performing a comprehensive pre-evaluation of the
extent of splenic embolization to achieving an accurate prediction of
splenic embolic volume. The extent of spleen volume that examined by CT
before and after embolization was 75% to 90%, which was consistent
with the pre-evaluation results. Therefore, we believe the degree of
splenic embolization can be precisely controlled by SPSE to achieve a
therapeutic effect of reducing hemolysis.
The white marrow of the spleen is an important component of the lymphoid
tissue in the body (Approximately 25%). It has germinal centers which
dominated by early B lymphocytes and plasma cells. Therefore, total
splenectomy can lead to a significant reduction in antibody production.
When foreign antigens are appeared in the circulation, the spleen
provides an essential place for the immune response9.
In this study, SPSE can effectively reduce the volume of the spleen and
maintain the immune function of the splenic white marrow to some extent.
The mild elevation of the complement system compared to the preoperative
period was considered an effect possibly relate to surgical
embolization10,11. The complement system exerts innate
immune by lysing or killing of bacteria, modulating phagocytosis or
participates in antibody-mediated specific immune responses. Our study
also showed that all splenic immune functions were maintained in the
normal range after SPSE and no surgery-related infection of SPSE during
the follow-up period. Thus, we demonstrated SPSE had a substantial
improvement in maintaining normal immune function than total
splenectomy. We are aware that the younger the patients with HS
diagnosis, the severer the symptoms of hemolytic anemia may have.
Considering the risk of post-splenectomy fulminant infection, many
patients with total splenectomy was significantly older. We believed
SPSE preserves normal immune function while treating HS, offers the
possibility of surgery in earlier ages and reduces the complications for
patients with HS.
All the post-embolization syndromes in this study are minor and
controllable, it mainly manifested by abdominal pain, fever and
vomiting. Most patients’ symptoms resolve within 1 week after surgery.
Previous studies have shown that common complications of total
splenectomy include postoperative infection, OPSI, surgical bleeding,
injury of adjacent organs and venous thromboembolism
(VTE)2,12,13. The most serious complications of PSE
are abdominal infection and spleen abscess formation, which is deadly
for patients in severe cases14. The cause of spleen
abscess formation includes excessive embolization which leads liquefied
necrosis of a large amount of spleen tissue and secondary bacterial
infection. There are two possible sources of bacteria, one of them is
interventional contamination, the other is that, the enteric-derived
bacteria which retained in the portal venous system reverse into the
spleen since the slow speed of flow in the splenic vein after massive
embolization of the splenic parenchyma15. However,
there is no patient had a splenic abscess in this study. The reason to
do this study is as following. Firstly, the number of patients is still
small. Secondly, SPSE achieved the purpose that accurately embolization
by the accurate selection of secondary arteries and narrowing the
possibility of infection caused by stagnation of splenic vein blood flow
which is the result of over embolization of splenic artery trunk.
Thirdly, the minified dosage of embolic agent during treatment also
indirectly diminishes the risk of contamination. The fact that there is
not any expose of significant flow stagnation or reflux in the splenic
artery angiogram after SPSE had been confirmed by the color
ultrasonography of the blood flow of splenic vein 3 days after the
procedure. In addition, triple cephalosporin was intravenously applied
within 48 hours postoperatively. Since these prophylactic anti-infection
actions were actively performed, the risk of splenic infection was
minimized by avoiding possible intraoperative contamination and
postoperative enterogenic infection to the greatest extent.
A few reports of previous study shown the growth of residual accessory
spleen after total splenectomy16, or growth of
residual spleen after partial splenectomy trigger recurrence of anemia
which requires secondary surgery17,18. In a long-term
follow-up study of partial splenectomy19, mild and
moderate hemolysis may be a long term symptoms after partial
splenectomy, and a small number of patients may be at risk of secondary
gallstones and hemolytic anemia. In our observed SPSE patients with a
median follow-up time of 19 months (8-26 months), there is no cases of
hemolytic anemia which requires transfusion therapy, only a few children
have mild hemolysis and all patients with SPSE recovered well after
surgery. We believe the better results were mainly becauseonly small
portion of the upper splenic (10%-20%) were preserved by the accurate
control of embolization, moreover, the growth of the normal residual
spleen was effectively limited by the blockage of diaphragm and
embolized spleen. In fact, since we preserved the splenic artery trunk
upfront, there is an opportunity to do another embolization as
re-intervention if symptomatic recurrence of anemia appeared at later
stage. The shortage of this study is the short follow-up period. Hence,
long-term follow-up should be applied to clarify the dynamic changes of
spleen volume and hemolysis after embolization.
In conclusion, SPSE is a feasible, safe and effective alternative to
splenectomy for childhood hereditary spherocytosis. SPSE may have
greater advantages on expanding the age range of surgery, reducing the
severity of surgical trauma, and minimizing the possibility of
infection. However, a longer follow-up period, a larger sample size, and
applying other indications such as hypersplenism, are mandatory for the
further assessment of SPSE.